Polymeric filament thinning and breakup in microchannels

The effects of elasticity on filament thinning and breakup are investigated in microchannel cross flow. When a viscous solution is stretched by an external immiscible fluid, a low 100 ppm polymer concentration strongly affects the breakup process, compared to the Newtonian case. Qualitatively, polymeric filaments show much slower evolution, and their morphology features multiple connected drops. Measurements of filament thickness show two main temporal regimes: flow- and capillary-driven. At early times both polymeric and Newtonian fluids are flow-driven, and filament thinning is exponential. At later times, Newtonian filament thinning crosses over to a capillary-driven regime, in which the decay is algebraic. By contrast, the polymeric fluid first crosses over to a second type of flow-driven behavior, in which viscoelastic stresses inside the filament become important and the decay is again exponential. Finally, the polymeric filament becomes capillary-driven at late times with algebraic decay. We show that the exponential flow thinning behavior allows a novel measurement of the extensional viscosities of both Newtonian and polymeric fluids.Comment: 7 pages, 7 figure

Lycia Trouton (Art Forum)

Dr Lycia Trouton is an Australian citizen who was born in Belfast. She lectured across theory and practice in Darwin & Adelaide, after working for a decade in Canada & the USA, primarily as a site-specific sculptor who utilised compressed organic materials. Trouton’s practice-led research engages in issues of monumentality and its opposite: the intimate art of memory. Her long-term work on the Canada Council of the Arts funded The (Irish) Linen Memorial has brought her into concerns with restorative justice, language and art, and for which she has just received a 'New Academic Research Grant' from UTAS. Prior to coming to Australia for her doctorate at Wollongong, Trouton was Artist-in-Residence at the University of B.C. sylviculture forest, Penn State University Berks campus, and the liberal art schools: Albright and Whitman College, USA, among other places, and with architect and landscape architect firms in Seattle. While completing her Doctorate (DCA) from the University of Wollongong, she held a Research Assistantship for an Australian Research Council large discovery grant on the intersection of text and the-art-of-textiles; her Masters (MFA) is in Sculpture from the Cranbrook Academy of Art in Michigan; her BFA (Hons) Sculpture is from Carnegie Mellon University, PA. Trouton's scholarly research includes an essay in the book, Echoes of Irish Australia: Rebellion to Republic, Eds. Dr. Jeff Brownrigg, Cheryl Mongan & Dr. Richard Reid (the latter is the senior curator of The National Museum of Australia's 2011 exhibition, The Irish in Australia, to open March 17th)

Decoupling the effects of shear and extensional flows on the alignment of colloidal rods

Cellulose nanocrystals (CNC) can be considered as model colloidal rods and have practical applications in the formation of soft materials with tailored anisotropy. Here, we employ two contrasting microfluidic devices to quantitatively elucidate the role of shearing and extensional flows on the alignment of a dilute CNC dispersion. Characterization of the flow field by micro-particle image velocimetry is coupled to flow-induced birefringence analysis to quantify the deformation rate--alignment relationship. The deformation rate required for CNC alignment is 4$\times$ smaller in extension than in shear. Alignment in extension is independent of the deformation rate magnitude, but is either 0$^\circ$ or 90$^\circ$ to the flow, depending on its sign. In shear flow the colloidal rods orientate progressively towards 0$^\circ$ as the deformation rate magnitude increases. Our results decouple the effects of shearing and extensional kinematics at aligning colloidal rods, establishing coherent guidelines for the manufacture of structured soft materials

Effectiveness and Adoption of a Drawing-to-Learn Study Tool for Recall and Problem Solving: Minute Sketches with Folded Lists

Drawing by learners can be an effective way to develop memory and generate visual models for higher-order skills in biology, but students are often reluctant to adopt drawing as a study method. We designed a nonclassroom intervention that instructed introductory biology college students in a drawing method, minute sketches in folded lists (MSFL), and allowed them to self-assess their recall and problem solving, first in a simple recall task involving non-European alphabets and later using unfamiliar biology content. In two preliminary ex situ experiments, students had greater recall on the simple learning task, non-European alphabets with associated phonetic sounds, using MSFL in comparison with a preferred method, visual review (VR). In the intervention, students studying using MSFL and VR had similar to 50-80% greater recall of content studied with MSFL and, in a subset of trials, better performance on problem-solving tasks on biology content. Eight months after beginning the intervention, participants had shifted self-reported use of drawing from 2% to 20% of study time. For a small subset of participants, MSFL had become a preferred study method, and 70% of participants reported continued use of MSFL. This brief, low-cost intervention resulted in enduring changes in study behavior